The present invention relates to a pneumatic tire suitable for traveling on icy and snow-covered roads, and more particularly to a pneumatic tire capable of effectively preventing wandering without impairing the wear resistance.
Pneumatic tires suitable for traveling on icy and snow-covered roads, including for example studless tires, usually have a square shoulder. In a square shoulder, as shown by a solid line in FIG. 7, an outer surface “a” of a shoulder block and a buttress face “b” extending radially inwardly and axially outwardly intersects at a ground contact edge “e” to form a substantial edge (corner). The term “substantial edge” means that the “square shoulder” encompasses a shoulder such that the ground contact edge “e” (corner “e”) is chamfered in the form of, for example, a small arc having a radius of about 2.0 mm or less. Such a tread portion can secure a large ground contact width TW and, therefore, a sufficient driving force can be obtained on an icy road. An example of the profile line of a round shoulder is shown in FIG. 7 by an imaginary line (dashed-two dotted line).
When traveling on a rutted road, pneumatic tires having square shoulders are easy to cause a so-called wandering phenomenon that a tire wanders by an external force or the like received from a road, since the ground contact edge “e” or a part of the buttress face “b” near the edge “e” comes into contact with a slope of a rut. Pneumatic tires capable of suppressing such a wandering are proposed, for example, in JP-A-6-087303 and JP-A-10-138713, but they leave room for improvement in wear resistance.
Accordingly, it is an object of the present invention to provide a pneumatic tire capable of suppressing occurrence of wandering phenomenon without impairing the wear resistance.
This and other objects of the present invention will become apparent from the description hereinafter.